CN104486992B - Magnetic resonance imaging apparatus and high frequency magnetic field conditional decision method - Google Patents

Magnetic resonance imaging apparatus and high frequency magnetic field conditional decision method Download PDF

Info

Publication number
CN104486992B
CN104486992B CN201380038419.XA CN201380038419A CN104486992B CN 104486992 B CN104486992 B CN 104486992B CN 201380038419 A CN201380038419 A CN 201380038419A CN 104486992 B CN104486992 B CN 104486992B
Authority
CN
China
Prior art keywords
area
region
high frequency
condition
magnetic field
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201380038419.XA
Other languages
Chinese (zh)
Other versions
CN104486992A (en
Inventor
金子幸生
羽原秀太
五月女悦久
尾藤良孝
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fujifilm Healthcare Corp
Original Assignee
Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Publication of CN104486992A publication Critical patent/CN104486992A/en
Application granted granted Critical
Publication of CN104486992B publication Critical patent/CN104486992B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/565—Correction of image distortions, e.g. due to magnetic field inhomogeneities
    • G01R33/5659—Correction of image distortions, e.g. due to magnetic field inhomogeneities caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
    • G01R33/34092—RF coils specially adapted for NMR spectrometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/385—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using gradient magnetic field coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/387—Compensation of inhomogeneities
    • G01R33/3875—Compensation of inhomogeneities using correction coil assemblies, e.g. active shimming

Abstract

In the MRI device using the transmit coil with multiple passages, efficiently and with height as the region of diagnosis is wanted in matter shooting.Possess：Region setting part, by the desired acquirement height in shooting area as the region of the image of matter is set as first area；With optimization portion, at least one party in the amplitude and phase of the high frequency waves sent respectively from multiple passages is determined as high frequency magnetic field condition, the high frequency magnetic field condition is determined in a manner of under the uniformity restriction condition that the uniformity of high frequency magnetic field distribution of the optimization portion in by the first area is set to more than setting and being set to below respective setting by least one party in specific absorption rate and the signal value in the region for producing illusion.

Description

Magnetic resonance imaging apparatus and high frequency magnetic field conditional decision method
Technical field
The present invention relates to magnetic resonance photography (MRI：Magnetic Resonance Imaging) technology, more particularly, to The irradiation technique of the high frequency magnetic field of the rotating excitation field of electromagnetic induction phenomenon is induced in generation.
Background technology
MRI device is the atomic nucleus in the arbitrary cross-section of crosscutting check object is caused magnetic resonance and is total to from caused magnetic Shake the medical diagnostic imaging apparatus of the layer image obtained in signal in the section.One kind as electromagnetic wave is sent to check object Rf wave (Radio Frequency wave, hereinafter referred to as RF), encourage check object in nuclear spin, Ran Houjie Receipts NMR signal caused by because of nuclear spin, by check object image conversion.Transmission to the RF of check object is to pass through RF With coil come what is completed, the reception of the NMR signal from check object is completed by RF receiving coils for transmission 's.
In recent years, there is the static magnetic field strength for the purpose of the SNR (Signal to Noise Ratio) of image raising Become big trend, start to have popularized High magnetic field MRI device (the super-high magnetic field MRI dresses that static magnetic field strength is more than 3T (tesla) Put).But although static magnetic field strength is more big more can improve SNR, it is irregular easily to produce the depth in photographed images. Because along with highfield, the RF used to induce electromagnetic induction phenomenon frequency uprises.For example, magnetostatic Field intensity is frequency of use 128MHz RF in 3T (tesla) MRI device (hereinafter referred to as 3T MRI devices).In organism Interior, the wavelength of the RF is 30cm or so, change can be produced in its phase substantially with belly section same levels.Pass through the phase The change of position, irradiation RF are distributed and because the RF is generated and induces rotating excitation field (the hereinafter referred to as high frequency magnetic of electromagnetic induction phenomenon Field distribution, B1) spatial distribution become uneven, can produce image disorder.Therefore, carried out in super-high magnetic field MRI device , it is necessary to reduce rotating excitation field B in RF irradiations1Technology pockety.
As reduction B1The uneven RF illuminating methods of distribution, there is the method for being referred to as " RF shimmings ".This is that one kind makes With the transmission coil with multiple passages, control is supplied to phase and the amplitude of the RF pulses of each passage to reduce shooting area B1Uneven method (for example, referring to patent document 1).Measure the B of each passage in advance before formally shooting (this pinch of picture)1 Distribution, uses the B1Distribution, calculate for reducing B1The amplitude and phase of uneven optimum RF pulse.Now, by section A part of region, i.e. want diagnosis region be set as Region Of Interest (ROI：Region of Interest), determine to be used for Reduce the uneven amplitudes of B1 and the phase in ROI.
In addition, it is also proposed that only improve the B in ROI1It is worth and reduces the B in other regions1The RF illuminating methods of value are (for example, ginseng According to non-patent literature 1).Wherein, using the B in the region in ROI and the region outside ROI1The ratio between average value, with the B in ROI1Value is most Big mode sets RF amplitude and phase.Thus, B is made1Concentration of local is distributed in ROI.
In addition, it is also proposed that more precisely control B by changing RF waveforms and leaning magnetic field waveform1The method of distribution (for example, referring to patent document 2).
Citation
Patent document
Patent document 1：No. 7078901 specifications of United States Patent (USP)
Patent document 2：No. 2003/0214294 specification please be disclose in United States Patent (USP)
Non-patent literature
Non-patent literature 1：Tamer S.Ibrahim etc. write, Understanding and manipulating the RF fields at high field MRI、NMR in Biomedicine、2009、pp.927-936
The content of the invention
The invention problem to be solved
In MRI device, because of highfield, because illusion (artifact) caused by the dynamic grade of body becomes more notable.This Outside, in MRI device, consider to the security of organism, it is specified that the uptake (SAR (Specific of the RF in organism Absorption Ratio)：Specific absorption rate) converge in prescribed limit.But due to the highfield of device, it is used RF frequency uprises, and SAR can also become big.
In the RF shimmings that patent document 1 or non-patent literature 1 are recorded, illusion and/or SAR can't be reduced to.Therefore, Cause to reacquire image etc. due to illusion, in order that SAR converge on as defined in when limiting checks sequence, shooting in scope Between, which hinders the efficiency of inspection.In addition, in the method that patent document 2 is recorded, the irradiation time of RF pulses is elongated, to arteries and veins Rush that sequence is restricted, may interfere with the efficiency of inspection.
The present invention completes in view of the foregoing, it is therefore intended that, in the MRI dresses using the transmit coil with multiple passages In putting, there is provided with the efficient and high technology that the region for wanting diagnosis is shot as matter.
Means for solving the problems
The present invention is by the B in Region Of Interest1Distribution at least reduces SAR and illusion while being set to uniformity more than regulation In a side.
Specifically, there is provided a kind of magnetic resonance imaging apparatus for possessing transmit coil, the transmit coil have respectively to Detected body sends multiple passages of high frequency waves, and the magnetic resonance imaging apparatus is characterised by possessing region setting part, will clapped The desired acquirement height taken the photograph in region is as the region of the image of matter is set as first area；With optimization portion, will be separately sent to more At least one party in the amplitude and phase of the high frequency waves of the individual passage is determined as high frequency magnetic field condition, and the optimization portion is with general The uniformity of high frequency magnetic field distribution in the first area is set to more than setting and by specific absorption rate and produces the area of illusion The mode that at least one party in the signal value in domain is set to below respective setting determines the high frequency magnetic field condition.
A kind of further it is provided that height for determining to be separately sent to multiple passages of the transmit coil of magnetic resonance imaging apparatus The high frequency magnetic field conditional decision method of at least one party in the amplitude and phase of frequency ripple, the spy of the high frequency magnetic field conditional decision method Sign is, including：By the desired acquirement height in shooting area as the region of the image of matter is set as that the region of first area is set Step；Be set to more than setting with the uniformity for being distributed the high frequency magnetic field in the first area and by specific absorption rate and The mode that at least one party in the signal value in the region of illusion is set to below respective setting is produced, decision is separately sent to more The optimization step of at least one party in the amplitude and phase of the high frequency waves of the individual passage.
Invention effect
, can be with high efficiency and high picture in the MRI device using the transmit coil with multiple passages according to the present invention The region of diagnosis is wanted in matter shooting.
Brief description of the drawings
Fig. 1 is the block diagram of the MRI device of embodiments of the present invention.
Fig. 2 (A) is the explanation figure for illustrating the transmit coil of embodiments of the present invention, and (B) is to be used to illustrate this hair The explanation figure of the shooting area of bright embodiment, (C) are for illustrating the phantom (phantom) in embodiments of the present invention The rotating excitation field B of interior generation1The explanation figure of the simulation result of distribution.
Fig. 3 is the functional block diagram of the computer of embodiments of the present invention.
Fig. 4 (A) is the explanation figure of the setting example of the first area and second area for illustrating embodiments of the present invention, (B) it is explanation figure for illustrating the setting example of the first area of embodiments of the present invention.
Fig. 5 is the flow chart of the shooting processing of embodiments of the present invention.
The setting example of first area and second area when Fig. 6 is the shooting belly for illustrating embodiments of the present invention Explanation figure.
The explanation figure of shooting area when Fig. 7 (A) is the shooting breast for illustrating embodiments of the present invention, (B) is For illustrate embodiments of the present invention shooting breast when first area and second area setting example explanation figure.
The explanation figure of shooting area when Fig. 8 (A) is the shooting shoulder for illustrating embodiments of the present invention, (B) is For illustrate embodiments of the present invention shooting shoulder when first area and second area setting example explanation figure.
Fig. 9 (A) is for illustrating the B in phantom during without RF shimmings1The explanation figure of distribution, (B) are existing for illustrating The B in phantom during RF shimmings in technology1The explanation figure of distribution, (C) are the uses for illustrating embodiments of the present invention The B in phantom during the first optimization of conditions1The explanation figure of distribution, (D) are that the use second of embodiments of the present invention is optimal The B in phantom during change condition1The explanation figure of distribution.
Figure 10 be indicate no RF shimmings, RF shimmings of the prior art in a tabular form, using the first optimization of conditions when With the B in the first area in phantom during the second optimization of conditions of use, each1Uniformity index USD, RF irradiation powers and The B of first area1The B of average value and second area1The explanation figure of the example of the ratio between average value.
Embodiment
Hereinafter, illustrate to apply embodiments of the present invention using accompanying drawing.In addition, in the institute for illustrating each embodiment Have in figure, same symbol is assigned to the part with same function, and omit explanation repeatedly.In addition, not by these limits The fixed present invention.
First, being monolithically fabricated for the MRI device of present embodiment is illustrated.Fig. 1 is the MRI device 100 of present embodiment Block diagram.As shown in the drawing, the MRI device 100 of present embodiment, which possesses, produces the magnet 101 of magnetostatic field, produces leaning magnetic field Coil 102, the unifluxor circle 112 for adjusting magnetostatic field uniformity, sequencer 104, the RF hairs of irradiation (transmission) high frequency magnetic field (RF) Send the RF receiving coils of the NMR signal caused by coil (transmit coil) 114, detection (reception) from detected body 103 (receiving coil) 115, carry the workbench 107 of detected body 103, leaning magnetic field power supply 105, high frequency magnetic field generator 106, connect Receive device 108, even magnetoelectricity source 113 and control each several part of MRI device 100 and realize the computer 109 of shooting.
Gradient magnetic field coil 102 and unifluxor circle 112 are connected with leaning magnetic field power supply 105 and even magnetoelectricity source 113 respectively.This Outside, transmit coil 114 and receiving coil 115 are connected with high frequency magnetic field generator 106 and receiver 108 respectively.
Sequencer 104 is according to the instruction from computer 109, to leaning magnetic field power supply 105, even magnetoelectricity source 113 and high frequency Magnetic field producer 106 sends order, produces leaning magnetic field and RF respectively.Irradiated by transmit coil 114 to detected body 103 (transmission) RF.Detected by irradiating (transmission) RF from NMR signal caused by detected body 103 by receiving coil 115 (reception), detection is carried out by receiver 108.Magnetic resonance frequency as the benchmark of the detection in receiver 108 is computer 109 Set via sequencer 104.The signal being detected is sent to computer 109 by A/D translation circuits, in computer The signal transactings such as Image Reconstruction are carried out in 109.Its result is shown in the display device 110 being connected with computer 109.It is detected Signal and measuring condition can be stored in as needed in the storage device 111 being connected with computer 109.
Magnet 101, unifluxor circle 112 and even magnetoelectricity source 113 form the magnetostatic field forming portion for forming magnetostatic field space.Tilt Field coil 102 and leaning magnetic field power supply 105 form the leaning magnetic field applying unit for applying leaning magnetic field to magnetostatic field space.This Outside, transmit coil 114 and high frequency magnetic field generator 106 form the high frequency magnetic field transmission that (transmission) RF is irradiated to detected body 103 Portion.Receiving coil 115 and receiver 108 form the signal of NMR signal caused by detection (reception) from detected body 103 Acceptance division.
The transmit coil 114 of present embodiment is the multi-channel coil for possessing the multiple passages for sending independent RF respectively. Fig. 2 (A) represents the example of the transmit coil 114 of present embodiment.Here, it is to possess 4 passages exemplified with transmit coil 114 The situation of 4 passages (4ch) coil of (114a, 114b, 114c, 114d).It is sent to each passage (114a, 114b, 114c, 114d) RF amplitude and phase independently set by computer 109 respectively.The high frequency magnetic field generator 106 of present embodiment along with Control from computer 109, via each passage (114a, 114b, 114c, 114d) possessed supply terminals (117a, 117b, 117c, 117d), independently send RF waveforms to each passage.In addition, in the figure, 116 be RF shields.
The computer 109 of present embodiment suppresses SAR or illusion, in order to efficiently obtain Region Of Interest ROI high picture Matter image, control each several part involved by the shooting of MRI device 100.In order to realize the control, the computer of present embodiment 109 as shown in Figure 3, possesses the imaging conditions configuration part 310 of setting imaging conditions, according to by imaging conditions configuration part 310 The imaging conditions of setting are come the formal image pickup part 320 that is formally imaged.In addition, imaging conditions configuration part 310 possesses shooting position Put configuration part 311, magnetostatic field shimming portion 312 and RF shimmings portion 313.
Camera position configuration part 311 sets camera position (shooting section).Implement scouting before formally image to sweep Retouch, utilize obtained positioning image to set shooting section.For example, the positioning image on display device 110 is shown in On, specifying for user's progress is accepted, specified position is set as to image section., can also be by each as shooting section Position, the characteristic point by predetermined position, i.e. on positioning image etc. is automatically made clue.In addition, will shooting it is disconnected and on The region of detected body 103 be referred to as shooting area.
In magnetostatic field shimming portion 312, distribution of static magnetic field is measured, is adjusted so that magnetostatic field is as uniform as possible.Via Even magnetoelectricity source 113 makes unifluxor circle 112 work, so as to be adjusted.In addition, in the feelings for the uniformity that need not adjust magnetostatic field Under condition, can not also possess magnetostatic field shimming portion 312, even magnetoelectricity source 113, unifluxor circle 112.
RF shimmings portion 313 carries out determining to be sent to the RF of each passage (114a, 114b, 114c, 114d) of transmit coil 114 Amplitude and phase at least one party RF shimmings processing.The RF shimmings portion 313 of present embodiment suppresses as described above At least one party in SAR and illusion, in order to efficiently obtain the high as matter image of Region Of Interest ROI, determine each RF amplitude with At least one party in phase.Hereinafter, by the RF shimmings portion 313 of present embodiment it is determining, be sent to each logical of transmit coil 114 The respective amplitudes of RF in road are referred to as high frequency magnetic field condition with least one party in phase.
In order to realize above-mentioned decision, the RF shimmings portion 313 of present embodiment possesses region setting part 301, condition configuration par 302nd, optimization portion 303 and condition storing section 304.
Before the structure that each several part of the RF shimmings processing of the present embodiment of the progress of RF shimmings portion 313 is realized in explanation, First briefly describe the RF illuminating methods that the transmit coil 114 of present embodiment is carried out.Here, illustrate shooting detected body The situation of 103 abdomen area.When shooting abdomen area, as shown in Fig. 2 (B), the shooting area 201 of detected body 103 is set.
Fig. 2 (C) shows the phantom 200 of the abdomen area for simulating detected body 103, is irradiated from transmit coil 114 During RF, the generation in phantom 200 rotating excitation field B1(B1Distribution) 202 electromagnetic-field simulation result.
In addition, in formal emulation, the B inside shooting area 2011Intensity is nondimensional, makes the maximum in phantom 200 B1Intensity turns into 1.The size of the x, y, z direction of principal axis of phantom 200 is 300mm, 200mm, 900mm respectively.This is to assume that life The shape simplified on the basis of the belly section of object.In addition, the physics value of phantom 200 is, conductance 0.6S/m is relative to be situated between Electric constant is 80.This is determined on the basis of it assume that the water phantom close with the physics value of organism.On being irradiated RF frequency, it is assumed that 3T MRI devices, be set to 128MHz.
In addition, supplied to each passage (114a, 114b, 114c, 114d) respective supply terminals (117a, 117b, 117c, 117d) Voltage to the sine waveforms shown in following formula (1).
[formula 11
In addition, A1, φ 1 represents to supply electricity to the amplitude and phase of passage 114a supply terminals 117a sine waveform voltages respectively Position, A2, φ 2 represent to supply electricity to the amplitude and phase of passage 114b supply terminals 117b sine waveform voltages, A3, φ 3 respectively Expression supplies electricity to the amplitude and phase of passage 114c supply terminals 117c sine waveform voltages respectively, and A4, φ 4 represents to supply respectively Supply electricity to the amplitude and phase of passage 114d supply terminals 117d sine waveform voltages.In addition, the B shown in Fig. 2 (C)1Distribution 202 In, A1, A2, A3, A4 are all set to 1, they are φ 1=0, φ 2=pi/2s, φ 3=π, φ 4=3 pi/2s by phase settings.This be by Referred to as QD (Quadrature Drive) RF illuminating methods, it is the RF illuminating methods of standard.
As QD irradiation, from each passage (114a, 114b, 114c, 114d) with identical amplitude, differ pi/2 respectively Phase send RF waveforms in the case of, as shown in Fig. 2 (C), in the shooting area 201 of phantom, B1The size of intensity has partially Difference, become uneven.This is the B for turning into problem in High magnetic field MRI device at present1It is uneven.
The RF shimmings portion 313 of present embodiment particularly wants to the region to be diagnosed (diagnosis to reduce in shooting area 201 Region) in B1It is uneven, adjust to each passage (114a, 114b, 114c, 114d) send RF amplitude (A1, A2, A3, A4) and phase (φ 1, φ 2, φ 3, φ 4), it is high frequency magnetic field condition by optimal amplitude and phase settings.Now, this embodiment party The RF shimmings portion 313 of formula alsos for suppressing SAR and at least one party in illusion and adjusting these parameters.
The RF shimmings portion 313 of present embodiment determines to want to obtain diagnosis of the height as the image of matter first in shooting area Region.In addition, inhibition zone is determined, as the region that the region of generation illusion or local SAR uprise in diagnostic region.Suppress Region is the region different from diagnostic region.Also, to improve the B in diagnostic region1Suppress SAR and illusion while uniformity In the mode of at least one party determine high frequency magnetic field condition.
Diagnostic region and inhibition zone are respectively set as first area ROI1 and second area by region setting part 301 ROI2.Respectively by accepting user on positioning image or high frequency magnetic field condition being set into initial value and the B that carries out1Distribution The region specified in measurement result is set.That is, region setting part 301 sets the firstth area according to the instruction from user Domain ROI1 and second area ROI2.First area ROI1 and second area when Fig. 4 (A) represents to specify belly as shooting position ROI2 setting example.
As the region for producing illusion, for example, setting fat region and heart area etc. have the dynamic region of periodic body. In addition, because for fat region, the signal intensity from fat is relatively big compared with its hetero-organization, therefore either Periodic or random body moves, and the contribution to illusion is all larger.
In addition, the first area ROI1 as diagnostic region and the second area ROI2 as inhibition zone can also be formed To be set automatically according to shooting position, shooting purpose.Now, MRI device 100 is also equipped with corresponding with position and shooting purpose First area ROI1 and second area ROI2 region storage unit is associatedly stored, if region setting part 301 is used as imaging conditions And set position and shooting purpose, then extracted and the shooting position set under imaging conditions or shooting mesh from region storage unit The corresponding first area ROI1 and second area ROI2 associatedly stored, set.Region storage unit is registered in advance Into storage device 111.
In addition, the region for producing illusion is not present in the ROI1 of first area or even if exists but is negligible generation Illusion degree in the case of, as shown in Fig. 4 (B), second area ROI2 can not also be selected.
Optimization portion 303 is in order to optimize the B in the ROI1 of first area1Distribution, will be sent to each passage (114a, 114b, 114c, 114d) RF amplitude (A1, A2, A3, A4) and phase (φ 1, φ 2, φ 3, φ 4) at least one party be determined as height Frequency magnetic field condition.In the present embodiment, as described above, in order that B in the ROI1 of first area1The uniformity of distribution is regulation More than value and at least one party in SAR and illusion is reduced, determine the high frequency magnetic field condition.In the present embodiment, by the high frequency Magnetic field condition is as solution when predetermined object function being set into minimum under predetermined restriction condition.
The calculating of solution using the solution of optimization problem, such as steepest descent method, gradient method, Newton method, least square method, Conjugate gradient method, linear programming technique, Nonlinear Programming Method, the value of amplitude and phase is changed exhaustively optimal to calculate Method of solution etc. is carried out.
In addition it is also possible to the value of amplitude and phase is set to change exhaustively to obtain the solution of the minimization of object function. For example, respectively by 1dB, 5 degree be unit change amplitude and phase value to calculate the value of object function, obtain when becoming minimum Amplitude and phase.But calculated when exhaustive changing amplitude and phase in the case that the time can increase, for example, it is also possible to Just start when the variable quantity of amplitude and phase is set it is larger in the state of obtain object function take minimum value amplitude and Phase, then near the value of the amplitude and phase, amplitude and phase are obtained in the state of variable quantity is reduced.Carry out these calculations The initial value of amplitude and phase during method is maintained in storage device 111 in advance.It is in addition, advance on optimal amplitude and phase In the case of a certain degree can be predicted, the predicted value can also be set to initial value, it is exhaustive only for the value near the initial value Ground changes amplitude and phase.
Again, optimization portion 303 can also measure the B in shooting area in change high frequency magnetic field condition every time1 The B of distribution1Distribution measuring, obtain the B in shooting area1Value.In addition it is also possible to only change the side in amplitude and phase to determine Determine high frequency magnetic field condition.
Condition storing section 304 stores restriction condition and mesh of the optimization portion 303 used in the calculating of high frequency magnetic field condition The group (optimization of conditions) of scalar functions.Condition configuration par 302 is extracted from condition storing section 304 and optimized according to the instruction of user Optimization of conditions of the portion 303 used in the calculating of high frequency magnetic field condition, and set.Set by optimization portion 303 utilizes Optimization of conditions calculate high frequency magnetic field condition.
It is alternatively, it is also possible to be configured to, optimization of conditions is corresponding with least one party in shooting position and shooting purpose Associatedly store in condition storing section 304, condition configuration par 302 stores according to the shooting position being set by the user from condition Optimization of conditions is extracted in portion 304, so as to automatically select, set optimization of conditions.
Fig. 5 represents the flow of the shooting processing of the processing of the RF shimmings including present embodiment based on these each functions.This The shooting processing of embodiment is started by the instruction of user's progress.
First, imaging conditions configuration part 310 is accepted including camera parameter, shooting position, shooting purpose etc. from user there The input of imaging conditions, and set (step S1001).Then, scout scan, setting are implemented in camera position configuration part 311 Camera position (step S1002).Then, region setting part 301 sets first area ROI1 and second area ROI2 (steps S1003).As described above, second area ROI2 can not also be set.
Then, condition configuration par 302 is extracted from condition storing section 304 and sets the group structure by object function and restriction condition Into optimization of conditions (step S1004).Obtained under the restriction condition that condition configuration par 302 is set in optimization portion 303 The optimization (step S1005) of solution when object function to be set to minimum.Then, the solution that imaging conditions configuration part 310 will be obtained As the RF for each passage being sent to used in shooting amplitude and phase, it is set as imaging bar together with other camera parameters Part (step S1006).
Then, formal image pickup part 320 is formally imaged according to the imaging conditions set by imaging conditions configuration part 310 (step S1007).
Each function that computer 109 is realized is that the possessed CPU of computer 109 will be pre-stored in storage device 111 In download program perform to realize into memory.In addition, the building condition storage part 304 on storage device 111.
Then, optimization of conditions (object function and restriction bar that present embodiment is stored in condition storing section 304 are illustrated The group of part) concrete example.In the present embodiment, according to shooting position and purpose, by the B in the ROI of Region Of Interest1What is be distributed is equal Once, SAR irradiation power, the B in the ROI of Region Of Interest are influenceed1Average value, in Region Of Interest produce illusion region in B1Any one in average value is used in object function and restriction condition.
Hereinafter, in the present embodiment, as the B represented in shooting area 2011The index of the uniformity of distribution, use The B represented by following formula (2)1It is distributed uniformity index USD。B1It is distributed uniformity index USDIt is B1The standard deviation divided by B of value1 Value obtained from average value.It may be said that the B1It is distributed uniformity index USDIt is smaller, the B in subject area1Distribution is more uniform.
[formula 2]
First, first optimization of conditions (the first optimization of conditions) is illustrated.In the first optimization of conditions, as target Function, use the index for the irradiation power for determining the RF based on each passage for being sent to transmit coil 114.Specifically, use The irradiation power index P represented by following formula (3)SUM.In addition, irradiation power index PSUMIt is destined to shaking for the RF of each passage The quadratic sum of width.
[formula 3]
PSUM=A12+A22+A32+A42...(3)
In addition, restriction condition is set to first area ROI1 B1It is distributed uniformity index USD_ROI1In setting UUBelow.Should Setting UUIt has been determined in advance as defined in can be achieved as the value of matter, condition storing section is stored in together with optimization of conditions In 304.Hereinafter, by first area ROI1 B1It is distributed uniformity index USD_ROI1In setting UUFollowing restriction condition is referred to as Uniformity restriction condition.
Therefore, if first optimization of conditions is set as into optimization of conditions, optimization portion 303 by condition configuration par 302 High frequency magnetic field condition is calculated as with the optimum solution of following formula (4).
[formula 4]
If the first optimization of conditions of selection simultaneously determines high frequency magnetic field condition, the first area ROI1 as diagnostic region B1It is distributed uniformity index USDIt is suppressed in because of uniformity restriction condition below setting.Therefore, first area ROI1 becomes Provide the uniformity of the above.In addition, the power P of the RF from the irradiation of each passageSUMBecome minimum.Therefore, for shooting area 201 Overall irradiation power becomes minimum, can suppress SAR.
Particularly, in the case of being not produce the region of illusion in the region beyond diagnostic region, it is able to maintain that diagnostic region Efficiently suppress SAR while the picture matter in domain.In addition, it need not now select second area ROI2.
Then, second optimization of conditions (the second optimization of conditions) is illustrated.In the second optimization of conditions, with following Formula (5) represents object function, is set to second area ROI2 B1Average value mean (B1_ROI2) with first area ROI1 B1It is average Value mean (B1_ROI1) the ratio between, mratio.As shown in formula (5), mratioIt is second area ROI2 B1Average value mean (B1_ROI2) remove With first area ROI1 B1Average value mean (B1_ROI1) obtained from value.Hereinafter, by mratioReferred to as B1Than.
[formula 5]
In addition, as restriction condition, foregoing uniformity restriction condition and the irradiation power index by shooting area are used PSUMIt is set to setting PUFollowing the two conditions of irradiation power restriction condition.The setting P of irradiation power restriction conditionUFrom peace The viewpoints such as full property are set out and are determined in advance, are stored in together with optimization of conditions in condition storing section 304.
Therefore, if setting the second optimization of conditions by condition configuration par 302 is used as optimization of conditions, optimization portion 303 calculate high frequency magnetic field condition, the optimum solution as following formula (6).
[formula 61
B1Represent the sensitivity of regional.Suppressed by the sensitivity relatively to inhibition zone, so as to reduce Relative to the signal intensity of the inhibition zone of the signal intensity of diagnostic region.Therefore, if selecting the second optimization of conditions and determining High frequency magnetic field condition, then due to B1Than minimum, therefore the signal from second area ROI2 can be suppressed, can relatively increased First area ROI1 signal.In addition, respectively by first area ROI1 B1It is distributed the irradiation work(of uniformity and shooting area 201 Rate suppresses below setting.Therefore, it is possible to which with height as matter shoots diagnostic region, and SAR can be suppressed.Further, since can be right The signal value of inhibition zone is suppressed, therefore can reduce the illusion of diagnostic region, can obtain the higher image as matter.
Particularly, it is being diagnosis pair close to the position at the position for easily producing illusion if using the second optimization of conditions As when, effectively suppress SAR while the picture matter for being able to maintain that diagnostic region.
Thus, for example can also with as shooting, position is corresponding with belly is associatedly stored in condition storing section 304 Second optimization of conditions.As noted previously, as its hetero-organization is big from the signal intensity ratio of fat, therefore the shadow of illusion is moved to body Sound is also big.Therefore, in the case where shooting belly, a large amount of existing regions (fat region) of the fat on belly top are set as Second area ROI2, high frequency magnetic field condition is determined according to the second optimization of conditions, so as to reduce the signal of fat region Value, can reduce illusion.
Now, by accurately selecting fat region and as second area ROI2, so as to more effectively Reduce the B of fat region1Than.Here, the setting of the first area ROI1 and second area ROI2 when Fig. 6 represents to shoot belly Example.Belly upper face is fatty a large amount of existing regions.Therefore, the region of belly upper face is set as second area ROI2.Thus, by accurately limiting second area ROI2 scope, it particularly effectively can only reduce and want to reduce letter Number value region.In addition, the system of selection as fat region, can also use the image of water fat separation and be specified by user Fat region, fat region can also be specified automatically by computer.
Then, the 3rd optimization of conditions (the 3rd optimization of conditions) is illustrated.In the 3rd optimization of conditions, object function It is set to the B represented by above-mentioned formula (6)1Than.In addition, restriction condition uses uniformity restriction condition and first area ROI1 B1It is flat Average mean (B1_ROI1) it is setting BLFirst area magnetic field restriction condition above.The rule of first area magnetic field restriction condition Definite value BLIt is determined in advance, and is stored in together with optimization of conditions in condition storing section 304.
Therefore, if setting the 3rd optimization of conditions by condition configuration par 302 is used as optimization of conditions, optimization portion 303 calculate solution of the high frequency magnetic field condition as following formula (7).
[formula 71
If the 3rd optimization of conditions of selection simultaneously determines high frequency magnetic field condition, due in B1Average value be setting more than this B under conditions of sample1Than minimum, therefore while can the signal value in the ROI1 of first area be maintained more than setting relatively Suppress second area ROI2 signal value.Therefore, it is possible to effectively suppress illusion.Further, since the B by first area ROI11 Distribution uniformity ensures more than regulation, therefore can shoot the region for wanting to diagnose as matter with height.
For example, also including easily producing illusion because periodic body is dynamic in addition to the diagnostic region of shooting area 201 Position in the case of, by periodic body move position be set as second area ROI2, it is possible thereby to be applicable the 3rd optimize article Part.Therefore, the 3rd optimization of conditions for example corresponding with the breast as shooting position can associatedly be stored in condition storing section In 304.Because when shooting breast, can include carrying out the dynamic heart of periodicity body in shooting area.
The figure of shooting area 201 when Fig. 7 (A) is for illustrating to shoot breast.By being set by camera position configuration part 311 Fixed camera position (shooting section) determines shooting area 201.In addition, Fig. 7 (B) is for illustrating being set by region now The first area ROI1 and second area ROI2 explanation figure that portion 301 is set.As shown in the drawing, breast area is set as first Region ROI1, heart area is set as second area ROI2.
Sent from each passage with the amplitude calculated according to above-mentioned 3rd optimization of conditions and the RF of phase, so as to breast The B in region (first area ROI1)1Uniformity is improved, and obtains signal value more than regulation.On the other hand, can press down The signal value of heart area (second area ROI2) processed.Therefore, it is possible to obtain the height for the illusion for reducing breast area as matter Image.
Then, the 4th optimization of conditions (the 4th optimization of conditions) is illustrated.In the 4th optimization of conditions, by target letter Number is set to first area ROI1 B1Inverse (1/mean (the B of average value1_ROI1)).In addition, restriction condition is restricted using uniformity Condition and the B by second area ROI21Average value mean (B1_ROI2) it is set to setting BUFollowing second area magnetic field restricts bar Part.
Therefore, if the 4th optimization of conditions is set as into optimization of conditions, optimization portion 303 by condition configuration par 302 High frequency magnetic field condition is calculated, the solution as following formula (8).
[formula 8]
According to the 4th optimization of conditions, for diagnostic region (first area ROI1), by B1The uniformity of distribution is set to With B among scope more than setting1The mode that average value becomes maximum determines high frequency magnetic field condition.In addition, it is directed to inhibition zone Domain (second area ROI2), with B1Average value is the mode below setting, determines high frequency magnetic field condition.Therefore, suppress to come from The signal value and reduction illusion of inhibition zone, and improve the picture matter of diagnostic region.In addition, object function now is not limited to Above-mentioned function.As long as illusion can be reduced.
4th optimization of conditions is for example applicable to the center of detected body 103 and off-center taken the photograph from what magnetic field center deviateed As in.Therefore, the 4th optimization of conditions for example corresponding with the shoulder as shooting position can associatedly be stored in condition In storage part 304.
The figure of shooting area 201 when Fig. 8 (A) is for illustrating to shoot shoulder.Set according to by camera position configuration part 311 Fixed camera position (shooting section) determines shooting area 201.In addition, Fig. 8 (B) is for illustrating being set by region now The first area ROI1 and second area ROI2 explanation figure that portion 301 is set.As shown in the drawing, the shoulder for imaging subject side is set It is set to first area ROI1, another shoulder is set as second area ROI2.
In addition, shooting shoulder when, as noted previously, as using height as matter shooting as image object side shoulder, because This progress configures the off-center of detected body 103 in a manner of the center (magnetic field center) that the shoulder is located at transmit coil 114 Shooting.Therefore, as shown in Fig. 8 (B), the shoulder regions for not being shooting object are difficult that local SAR is easy close to transmit coil 114 Uprise.
Therefore, as using local SAR reduction as purpose optimization of conditions restriction condition, can also be by the 5th most Goodization condition is accordingly stored with shoulder, and the 5th optimization of conditions is using uniformity restriction condition and will think from close Reduce the passage in the region of local SAR, the irradiation power for the RF that passage i.e. near second area is sent be set to setting with Under partial power's restriction condition.Now, object function is identical with the 4th optimization of conditions.
For example, as shown in Fig. 8 (B), if by the passage close with the region of desired reduction local SAR be set to passage 114b and Passage 114c, then by the irradiation power sum (A of these passages2 2+A3 2) it is set to setting AUBelow.Setting AUBy true in advance It is fixed, and be stored in together with optimization of conditions in condition storing section 304.
Therefore, if the 5th optimization of conditions now is set as into optimization of conditions by condition configuration par 302, optimize Solution of the portion 303 as following formula (9), determine to be sent to the RF of each passage amplitude and phase.
" formula 91
In addition, object function is set to from the passage close with the region (second area ROI2) of desired reduction local SAR The RF of transmission irradiation power sum, it is corresponding with shoulder associatedly to store the 6th optimization of conditions, the 6th optimization of conditions Used second area ROI2 SAR (SAR as restriction condition together with uniformity restriction conditionROI2) it is set to setting SARUFollowing SAR restriction conditions.The setting SAR of SAR restriction conditionsUIt is determined in advance, and is deposited together with optimization of conditions Storage is in condition storing section 304.
If thus, for example, the passage close with the region of desired reduction local SAR is set to passage 114b and passage 114c, then now optimization portion 303 determines solution of the high frequency magnetic field condition as following formula (10).
[formula 10]
In addition, now, such as according to B1It is distributed to speculate second area ROI2 SAR.In addition it is also possible to utilize electromagnetic field Emulate to calculate second area ROI2 SAR.In the case where being calculated using electromagnetic-field simulation, it can use and utilize meter The method of the result of SAR distributions in manikin etc. is calculated.
Shoulder as shooting object is set as first area ROI1, by the close transmit coil 114 of another shoulder Region be set as second area ROI2.Now, have from the transmission of each passage is above-mentioned according to the 5th or the 6th optimization of conditions The amplitude and the RF of phase calculated, so as to using as the B in the shoulder regions (first area ROI1) of shooting object1Uniformity Setting is ensured, another irradiation power of shoulder regions (second area ROI2) nearby can be suppressed.
Therefore, if selecting the 5th or the 6th optimization of conditions and determining high frequency magnetic field condition, the B of diagnostic region1It is homogeneous Spend for that more than setting and can suppress to the irradiation power near inhibition zone, therefore the picture matter of diagnostic region can be improved And reduce local SAR.
Then, the 7th optimization of conditions (the 7th optimization of conditions) is illustrated.In the 7th optimization of conditions, object function Using following formula (11) expression to irradiating power index PSUMAnd B1Than the index for assigning weight and combining.Hereinafter, this is referred to Nominally make synthesis index.
[formula 11]
αPSUM+βmratio...(11)
Wherein, alpha+beta=1.In addition, α and β is set by the user according to which side is paid attention to.Or can also be by each Shooting position predefines.Restriction condition uses uniformity restriction condition.
Therefore, if the 7th optimization of conditions is set as into optimization of conditions, optimization portion by condition configuration par 302 303 calculate high frequency magnetic field condition, the optimum solution as following formula (12).
[formula 12]
If the 7th optimization of conditions of selection simultaneously determines high frequency magnetic field condition, when can obtain the first optimization of conditions of selection and Select each effect during the second optimization of conditions.In addition, according to set coefficient, the degree of the effect can be adjusted.
In addition, the optimization of conditions being stored in condition storing section 304 is not limited to above-mentioned 7.As long as diagnosis will be used as B in the first area ROI1 in region1The uniformity of distribution is set to more than regulation grade, and can effectively obtain and vacation can be achieved The reduction of elephant and the solution of at least one party in SAR suppression.In addition it is also possible to by the grade of illusion and SAR grade At least one party be set to below setting, and the B in achievable first area ROI1 can be obtained1The raising of the uniformity of distribution Solution.
Hereinafter, by the simulation result of the RF shimmings of present embodiment and RF shimmings of the prior art and without RF shimmings Situation is contrasted.
Here, the RF coils of 4 passages shown in Fig. 2 (A) are used as transmit coil 114, for simulating detected body 103 Phantom 200, when representing to have irradiated RF in phantom 200 generation rotating excitation field B1Electromagnetic-field simulation result.It is used It is identical when the specification of phantom 200 is with Fig. 2 (C) electromagnetic-field simulation.In addition, irradiation RF frequency is similarly 128MHz.There is provided Sine waveforms to each supply terminals (117a, 117b, 117c, 117d) are also identical.
When Fig. 9 (A) is no RF shimmings, i.e. to set by the respective amplitudes of RF for being sent to each passage and the direct use of phase Initial value when B1It is distributed 401 (case A).
Fig. 9 (B) is when having carried out RF shimmings of the prior art (RF shimmings of the prior art), i.e. with by the firstth area B in the ROI1 of domain1The mode of distribution uniformity optimizes B during each RF amplitude and phase1It is distributed 402 (case B).In addition, B1 The index of uniformity has used the U shown in above-mentioned formula (2)SD。
Fig. 9 (C) is that the first optimization of conditions of present embodiment is set into optimization of conditions and has optimized shaking for each RF B when width and phase1403 (case C) are distributed, Fig. 9 (D) is to be set to the second optimization of conditions of present embodiment to optimize bar Part and B when having optimized each RF amplitude and phase1It is distributed 404 (case D).
In addition, in the emulation shown in Fig. 9, it is identical with Fig. 2 (C), with the maximum B in the phantom 200 in Fig. 9 (A)1Intensity Zero dimension (No dimensions, dimensionless are carried out as 1 mode).
In addition, during shown in Fig. 9 (A)~Fig. 9 (D), 4 RF illuminating methods are illustrated in Figure 10 table 500 each The B in the ROI1 of first area in phantom 2001Uniformity index USD, RF irradiation powers PSUM、B1Compare mratio.In addition, by Fig. 9 (A) without RF shimmings when (case A) RF irradiation powers PSUMIt is set to 100% and is used as benchmark.In addition, by B1Than being set to first B in the ROI1 of region1Average value and the B outside the ROI1 of first area1The ratio between average value.Due to being the B1 distributions of origin object, therefore B1Than for 1.
As shown in Fig. 9 (B), by RF shimmings of the prior art, the B in the ROI1 of first area1Distribution becomes most uniform. But under RF shimmings in the prior art, the B in the region outside uncontrollable first area ROI11。
On the other hand, as shown in Fig. 9 (C), it is known that if carrying out RF shimmings according to the first optimization of conditions of present embodiment, Then with the B of the bottom of phantom 2001Compare, the B on phantom top1It is suppressed smaller.In addition, as shown in Fig. 9 (D), it is known that if root According to present embodiment the second optimization of conditions carry out RF shimmings, then with the B of the bottom of phantom 2001Compare, the B on the top of phantom 2001 It is suppressed smaller.
In addition, as shown in Figure 10 table 500, if will be without RF shimmings when (case A) situation consider on the basis of, existing In the situation (case B) of the RF shimmings of technology, USDDiminish, the B in the ROI1 of first area1Distribution becomes uniform.But RF irradiates Power PSUMDo not change compared with (case A) when without RF shimmings.
In the case of the RF shimmings (case C) of the first optimization of conditions, USDU during than without RF shimmings (case A)SD It is also small, and RF irradiation powers are changed into 51.9%.Thus, it can be known that pass through the RF shimmings according to the first optimization of conditions, B1It is homogeneous Degree is improved, and reduces overall SAR (SAR of organism overall absorption).
As described above, under the first optimization of conditions, in restriction condition, the U in the ROI1 of first areaSDIt is configured to In or less than can realize it is more than regulation as the value (U of matterU).Therefore, by carrying out RF shimmings according to the first optimization of conditions, Can obtain can realize it is more than regulation as the B of matter1Uniformity, and SAR can be reduced half.In addition, in present case, will The U during RF shimmings of 2 passages is carried outSDValue (0.167) be set to UU.That is, by controlling the RF parameters of 4 passages, so as to real B during existing 2 passage1SAR can be reduced half while uniformity.
In the situation (case D) according to the RF shimmings of the second optimization of conditions, USDU during than without RF shimmings (case A)SD It is also small, and B1Compare mratioBecome minimum.By first area ROI1 B1In the case that average value is set to 1, second area B in ROI21Average value becomes 0.48, it is known that can reduce the B on the top of phantom 200 for being set as second area ROI21Value.By This, can suppress the illusion as caused by the top of phantom 200.
As described above, the MRI device 100 of present embodiment possesses with respectively to the more of detected body transmission high frequency waves The transmit coil of individual passage, the MRI device 100 are characterised by possessing：Region setting part 301, by wanting in shooting area Obtain high as the region of the image of matter is set as first area；With optimization portion 303, multiple passages will be separately sent to At least one party in the amplitude and phase of high frequency waves is determined as high frequency magnetic field condition, and the optimization portion 303 is with by described first The uniformity of high frequency magnetic field distribution in region is set to more than setting and by specific absorption rate and the signal in the region for producing illusion The mode that at least one party in value is set to below respective setting determines the high frequency magnetic field condition.
The optimization portion 303 can also be by the region of the uniformity, the specific absorption rate and the generation illusion At least one in signal value is set to restriction condition in advance, and at least one in rest parameter is set into object function in advance, as Optimize the solution of the object function and calculate the high frequency magnetic field condition, then determined.In addition, the region setting Portion 301 can also by the shooting area be different from the first area, including producing the region of the illusion Region or the region that uprises of specific absorption rate be further set to second area.
Thus, can be by the region of desired diagnosis, i.e. first area ROI1 B according to present embodiment1It is distributed uniformity Index USDSuppress below setting.Therefore, first area ROI1 is able to ensure that defined uniformity.In addition, according to optimization Condition, by the RF irradiated from each passage power PSUMIt is suppressed to below minimum or setting.Therefore, it is possible to suppress SAR.This Outside, for example, region outside diagnostic region, is set as second area ROI2 according to purpose, reduces the B in the region1Value is shone Penetrate power.For example, second area ROI2 will be set as to the big region that has an impact of illusion, if reducing B1Value, it becomes possible to Efficiently reduce illusion.In addition, the region for producing local high SAR is set as second area ROI2, if reducing irradiation work( Rate, it becomes possible to efficiently reduce local SAR.
Therefore, according to present embodiment, the region of diagnosis can be wanted as matter is shot with height, and determine to reduce SAR or vacation The irradiation RF parameters of at least one party as in.Also, shot according to the parameter, therefore can efficiently obtain and want to examine The height in disconnected region is as the image of matter.
In addition, in the above-described embodiment, in optimization processing, calculated the solution of each the minimization of object function, But be not restricted to that this.For example, it is also possible to be configured to, each object function is respectively set as to the inverse of above-mentioned each object function, Calculate and maximumlly solve the inverse.Alternatively, it is also possible to be configured to assign each index negative symbol, calculate the index most The solution changed greatly.
In addition, above-mentioned embodiment can also and with the application of the presaturation pulse used to reduce illusion.For example, As shown in Fig. 9 (D), equably irradiating the latter half region (first area ROI1) of section and suppressing upper half as far as possible In the case of the signal in domain (second area ROI2), to upper half area illumination presaturation pulse.
Presaturation pulse illusion when equably being irradiated in the upper half area as irradiation object region as far as possible reduces Effect is higher.Therefore, when irradiating presaturation pulse, it is expected to make the subregional B of the first half as far as possible1Distribution becomes uniform side Formula calculates RF parameters.That is, if it is set to second area ROI2 B1 uniformities (USD_ROI2), then object function is set as following Formula (13), calculate the RF parameters of presaturation pulse.
[formula 13]
min(USD_ROI2)...(13)
Then, as described above so that the B in the latter half region (first area ROI1)1The RF parameters being evenly distributed, Irradiation applies the postimpulse driving pulse of presaturation.Thus, by presaturation pulse and driving pulse come using each optimal RF parameters, so as to which illusion reducing effect becomes higher.
In addition, in the above-described embodiment, 1 first area ROI1 as diagnostic region of setting respectively has been illustrated And the situation of the second area ROI2 as inhibition zone, but be not restricted to that this.It can set respectively multiple.For example, remote In the case that the opening position in the desired region for reducing illusion has multiple positions, first area and second is set at each position Region.By so forming, it further can locally suppress B1Value, can efficiently reduce illusion.
In addition, now, such as set as the 4th optimization of conditions the B to inhibition zone1What average value was suppressed , can also be by the setting B of restriction condition for each region of multiple inhibition zones in the case of restriction conditionUIt is set as Different values.I.e., it is possible to weight is applied to restriction condition according to the position of inhibition zone.
In addition, in the above-described embodiment, situation of the shooting area for two dimension is generally illustrated, but in the situation of three-dimensional Under optimal high frequency magnetic field condition can be also obtained by same method.
In addition, in the above-described embodiment, the transmit coil of 3T MRI devices and 4 passages has been illustrated, but MRI is filled The composition put is not limited to this.The magnetic field higher than 3T, the port number transmit coil more than 4 passages can also be used.
In addition, in the above-described embodiment, the possessed computer 109 of MRI device 100 includes RF shimmings portion 313, calculate At least one party in optimal RF amplitude and phase, but be not restricted to that this.For example, it is also possible to can be with computer 109 RF shimmings portion 313 is constructed on the computer independently of MRI device 100 of transceiving data.It is identical with condition storing section 304, also may be used Not to be on the storage device 111 possessed in MRI device 100, but on the addressable independent storage device of computer 109 Construct.
In addition, the method for present embodiment goes for using in the medical various field of photography as purpose.
Symbol description
100：MRI device；101：Magnet；102：Gradient magnetic field coil；103：Detected body；104：Sequencer；105：Incline Oblique magnetic field power supply；106：High frequency magnetic field generator；107：Workbench；108：Receiver；109：Computer；110：Display device； 111：Storage device；112：Unifluxor circle；113：Even magnetoelectricity source；114：Transmit coil；114a：Passage；114b：Passage；114c： Passage；114d：Passage；115：Receiving coil；117a：Supply terminals；117b：Supply terminals；117c：Supply terminals；117d：Supply terminals； 200：Phantom；201：Shooting area；202：B1Distribution；301：Region setting part；302：Condition configuration par；303：Optimization portion； 304：Condition storing section；310：Imaging conditions configuration part；311：Camera position configuration part；312：Magnetostatic field shimming portion；313：RF Shimming portion；320：Formal image pickup part；401：B1Distribution；402：B1Distribution；403：B1Distribution；404：B1Distribution；500：Form； ROI1：First area；ROI2：Second area.

Claims (15)

1. a kind of magnetic resonance imaging apparatus, possesses transmit coil, the transmit coil has sends high frequency waves to detected body respectively Multiple passages, the magnetic resonance imaging apparatus is characterised by possessing：
Region setting part, the predetermined region in shooting area is set as first area；With optimization portion, will send out respectively At least one party being sent in the amplitude and phase of the high frequency waves of multiple passages is determined as high frequency magnetic field condition,
The optimization portion is set to more than setting and will compared with the uniformity for being distributed the high frequency magnetic field in the first area The mode that at least one party in the signal value in the region of absorptivity and generation illusion is set to below respective setting determines described High frequency magnetic field condition.
2. magnetic resonance imaging apparatus according to claim 1, it is characterised in that
The optimization portion by the uniformity, the specific absorption rate and produce the illusion region signal value at least One value is set to restriction condition, and by the uniformity, the specific absorption rate and produce the illusion region signal value In other values in it is at least one be set to object function, determine the high frequency magnetic field condition as optimizing the object function Solution.
3. magnetic resonance imaging apparatus according to claim 2, it is characterised in that
The restriction condition is that the uniformity is set into more than setting condition,
The object function is will be described by the way that the irradiation power for being sent to the high frequency waves of multiple passages is set into minimum Specific absorption rate is set to the function below setting.
4. magnetic resonance imaging apparatus according to claim 2, it is characterised in that
The region setting part will also be different from the first area and including producing the illusion in the shooting area The region that region or specific absorption rate including region uprise further is set to second area.
5. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
The optimization portion is so that the signal value in the first area is maintained more than setting and relative to described first The signal value in region and relatively suppress the mode of the signal value in the second area, determine the restriction condition and the mesh Scalar functions.
6. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
The restriction condition is that the uniformity is set into more than setting condition,
The object function is by by the height in the average value of the high frequency magnetic field in the first area and the second area The ratio between the average value in frequency magnetic field minimizes the function being set to the signal value of the second area below setting.
7. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
The restriction condition is that the uniformity is set into more than setting condition,
The object function is by the way that the average value of the high frequency magnetic field in the first area is maximized secondth area The signal value in domain is set to the function below setting.
8. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
The restriction condition is that the uniformity is set into putting down more than setting and by the high frequency magnetic field in the second area Average is set to below setting for the signal value of the second area to be set to the condition below setting.
9. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
The object function is the high frequency magnetic field that will be sent from the passage near the second area among multiple passages Irradiation power sum minimize the specific absorption rate be set to function below setting,
The restriction condition is the uniformity to be set to more than setting and by the organism uptake of the second area SAR is set to the condition below setting.
10. magnetic resonance imaging apparatus according to claim 2, it is characterised in that be also equipped with：
Condition storing section, store the optimization portion the high frequency magnetic field condition calculating used in the restriction condition and The object function；With
Condition configuration par, according to the instruction of user, extract and set used in the optimization portion from the condition storing section Restriction condition and object function.
11. magnetic resonance imaging apparatus according to claim 10, it is characterised in that
Position is corresponding associatedly stores the restriction condition and the object function with shooting for the condition storing section,
The condition configuration par is extracted from the condition storing section according to the shooting position being set by the user and sets the restriction Condition and the object function.
12. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
The region setting part sets the first area and the second area according to the instruction from user.
13. magnetic resonance imaging apparatus according to claim 4, it is characterised in that
Fat region or periodic body are moved region and are set as the second area by the region setting part.
14. magnetic resonance imaging apparatus according to claim 2, it is characterised in that
The optimization portion uses steepest descent method, gradient method, Newton method, least square method, conjugate gradient method, linear programming Method, Nonlinear Programming Method, by exhaustive change amplitude and phase value it is at least one in the method for optimum solution to calculate Method, calculate the solution.
15. a kind of high frequency magnetic field conditional decision method, determine to be separately sent to the multiple of the transmit coil of magnetic resonance imaging apparatus At least one party in the amplitude and phase of the high frequency waves of passage, the high frequency magnetic field conditional decision method be characterised by, including：
Zone enactment steps, the predetermined region in shooting area is set as first area；With
Step is optimized, the uniformity that the high frequency magnetic field in the first area is distributed is set to more than setting and will compared At least one party in the signal value in the region of absorptivity and generation illusion is set to the mode below respective setting, determines difference At least one party being sent in the amplitude and phase of the high frequency waves of multiple passages.
CN201380038419.XA 2012-08-03 2013-07-24 Magnetic resonance imaging apparatus and high frequency magnetic field conditional decision method Active CN104486992B (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2012173348 2012-08-03
JP2012-173348 2012-08-03
PCT/JP2013/070087 WO2014021172A1 (en) 2012-08-03 2013-07-24 Magnetic resonance imaging device, and determination method for high-frequency magnetic field conditions

Publications (2)

Publication Number Publication Date
CN104486992A CN104486992A (en) 2015-04-01
CN104486992B true CN104486992B (en) 2017-11-24

Family

ID=50027850

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201380038419.XA Active CN104486992B (en) 2012-08-03 2013-07-24 Magnetic resonance imaging apparatus and high frequency magnetic field conditional decision method

Country Status (5)

Country Link
US (1) US10451701B2 (en)
JP (1) JP5885845B2 (en)
CN (1) CN104486992B (en)
DE (1) DE112013003860T5 (en)
WO (1) WO2014021172A1 (en)

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5797765B2 (en) * 2011-09-29 2015-10-21 株式会社日立メディコ Magnetic resonance imaging apparatus, high-frequency magnetic field irradiation method, and program
DE102012215255B3 (en) * 2012-08-28 2014-02-27 Siemens Aktiengesellschaft Control of a magnetic resonance system taking into account current component-related B1 field maximum values
WO2015159664A1 (en) * 2014-04-16 2015-10-22 株式会社 日立メディコ Nuclear magnetic resonance imaging device and rf shimming method
US10330752B2 (en) 2015-03-06 2019-06-25 Hitachi, Ltd. Magnetic resonance imaging apparatus and method for setting RF shimming parameters
WO2016157063A1 (en) * 2015-03-27 2016-10-06 Koninklijke Philips N.V. Magnetic resonance volume coil with multiple independent transmit receive channels and method of operation thereof
JP6408954B2 (en) * 2015-05-14 2018-10-17 株式会社日立製作所 Magnetic resonance imaging apparatus, information processing apparatus, and high-frequency magnetic field shimming method
JP6513493B2 (en) * 2015-06-05 2019-05-15 株式会社日立製作所 Magnetic resonance imaging system
DE102015223897A1 (en) * 2015-12-01 2017-06-01 Siemens Healthcare Gmbh Method for magnetic resonance imaging
JP5943159B2 (en) * 2016-01-04 2016-06-29 株式会社日立製作所 Magnetic resonance imaging system
DE102016207368A1 (en) * 2016-04-29 2017-11-02 Siemens Healthcare Gmbh Method for forming RF pulses for the compensation of inhomogeneities in the edge region of an MR system
JP6280591B2 (en) * 2016-05-06 2018-02-14 株式会社日立製作所 Magnetic resonance imaging system
JP2019070583A (en) * 2017-10-10 2019-05-09 日本電信電話株式会社 Magnetic resonance observation device
CN115561687B (en) * 2022-10-13 2023-04-07 兰州大学 Method and system for optimizing radio frequency heating of implanted medical equipment in MRI

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102498411A (en) * 2009-09-17 2012-06-13 皇家飞利浦电子股份有限公司 Concurrent optimization of rf power and rf field uniformity in mri

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7136695B2 (en) * 2001-10-12 2006-11-14 Pless Benjamin D Patient-specific template development for neurological event detection
US6879158B2 (en) 2002-05-17 2005-04-12 General Electric Company Method for accelerating focused excitation with multiple RF transmit coils
DE102004013422B4 (en) 2004-03-18 2009-02-19 Siemens Ag Method for homogenizing a B1 field, magnetic resonance system and computer program product
CN105182263A (en) * 2008-04-28 2015-12-23 康奈尔大学 Accurate quantification of magnetic suceptibility in molecular mri
US8319496B2 (en) * 2009-04-01 2012-11-27 Yigitcan Eryaman Magnetic resonance method and apparatus for reducing RF heating in the patient
WO2010120829A2 (en) * 2009-04-14 2010-10-21 The Board Of Trustees Of The Univerisity Of Illinois Method for reducing artifacts in magnetic resonance imaging
KR101364527B1 (en) * 2011-12-27 2014-02-19 삼성메디슨 주식회사 Ultrasound system and method for providing motion profile information of target object

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102498411A (en) * 2009-09-17 2012-06-13 皇家飞利浦电子股份有限公司 Concurrent optimization of rf power and rf field uniformity in mri

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
7T body MRI:B1 shimming with simultaneous SAR reduction;Bob van den Bergen et al.;《PHYSICS IN MEDICINE AND BIOLOGY》;20070821;第52卷;第5430-5439页 *
Adiabatic B1 Shimming Algorithm for Multiple Channel Transmit at 7T;P.Balchandani et al.;《Proc. Intl. Soc. Mag. Reson. Med.》;20111231;第2907页 *

Also Published As

Publication number Publication date
JP5885845B2 (en) 2016-03-16
WO2014021172A1 (en) 2014-02-06
US10451701B2 (en) 2019-10-22
JPWO2014021172A1 (en) 2016-07-21
DE112013003860T5 (en) 2015-04-23
CN104486992A (en) 2015-04-01
US20150241539A1 (en) 2015-08-27

Similar Documents

Publication Publication Date Title
CN104486992B (en) Magnetic resonance imaging apparatus and high frequency magnetic field conditional decision method
JP6101352B2 (en) Magnetic resonance imaging apparatus and imaging parameter determination method
Padormo et al. Parallel transmission for ultrahigh‐field imaging
CN105988097B (en) For the method and magnetic resonance equipment of magnetic resonance imaging
US20130335080A1 (en) Resonance imaging apparatus and diffusion weighted image acquiring method thereof
JP6332891B2 (en) Parallel multi-slice MR imaging to suppress sideband artifacts
CN107072592A (en) MR imaging apparatus and quantitative magnetic susceptibility matching process
US20160116560A1 (en) Mr imaging with enhanced susceptibility contrast
US10024936B2 (en) System and method for electromagnet coil construction
CN106796273A (en) With the visual magnetic resonance imaging of enhanced bone
EP1425598A1 (en) Magnetic resonance apparatus with excitation antennae system
WO2016021603A1 (en) Magnetic resonance imaging device, and magnetic resonance imaging method
US20200408866A1 (en) Emulation mode for mri
CN103282790A (en) Fast dual contrast mr imaging
JP2015154911A (en) magnetic resonance imaging apparatus
WO2009081786A1 (en) Magnetic resonance imaging device and magnetization rate enhancement image picking-up method
CN103874457A (en) Magnetic resonance imaging equipment, high frequency magnetic field irradiation method and program
US10139462B2 (en) Magnetic resonance imaging apparatus and magnetic resonance spectroscopic method using the same
CN108027410A (en) Radio-frequency antenna component for the treatment of guide of magnetic resonant image
EP2741097A1 (en) Method and apparatus for acquiring B1 magnetic field phase information
CN106028928B (en) NMR imaging device and RF method for shimming
JP6513493B2 (en) Magnetic resonance imaging system
JP5460264B2 (en) Magnetic resonance imaging apparatus and operation control method of magnetic resonance imaging apparatus
Kroboth On the employment of matrix gradient coils for novel spatial encoding and magnetic field shimming in magnetic resonance imaging
Andrade Optimizing a RF Coil for Prostate Imaging at 7 Tesla MRI

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
C41 Transfer of patent application or patent right or utility model
TA01 Transfer of patent application right

Effective date of registration: 20160721

Address after: Tokyo, Japan, Japan

Applicant after: Hitachi Ltd.

Address before: Japan Tokyo Chiyoda District Kanda four chome 14 No. 1

Applicant before: Hitachi Medical Corporation

GR01 Patent grant
GR01 Patent grant
TR01 Transfer of patent right
TR01 Transfer of patent right

Effective date of registration: 20211123

Address after: Chiba County, Japan

Patentee after: Fujifilm medical health Co.,Ltd.

Address before: Tokyo, Japan

Patentee before: Hitachi, Ltd.